Magnetic recording media are typically formed on a substrate, such as a nickel-plated aluminum substrate, and deposited on the substrate are a plurality of layers, such as a chromium underlayer, a magnetic recording layer, and a protective overcoat. The magnetic recording layer may be formed of multiple magnetic films separated by a non-magnetic isolation layer, such as a thin chromium interlayer (Katayama, WP, Hata).
Typically, magnetic recording media are formed in a sputtering apparatus having a series of sputtering chambers, each with a sputtering target for material deposition. A substrate is placed in a first sputtering chamber, and a film or layer is deposited onto the substrate. The coated substrate is then shuttled to the next sputtering chamber, downstream from the first chamber, where another layer is deposited. The coated substrate is moved progressively from one chamber to the next for sputter deposition of each layer in the medium.
This process of fabricating media requires a plurality of sputtering chambers, one for each layer deposited. Depending on the number of layers in the medium and the composition of each layer, the number of chambers required may exceed the number in a typical sputtering apparatus.
Another drawback to this method of sputtering is the large inventory of materials, such as sputtering targets, needed. This is especially the case where a medium having two layers formed of the same material is formed by sputtering that material in separate chambers; each chamber requiring a sputtering target.
Another disadvantage to sputtering multiple layers in separate sputtering chambers is the dwell time of the substrate, that is the time between completing sputtering in one chamber and beginning sputtering in the next chamber. The substrate cools during this time, and the first layers are deposited at higher substrate temperatures than later layers in the medium. The different deposition temperatures affects the magnetic recording properties of the medium, especially for magnetic layers. Media having magnetic layers sputtered at higher temperatures have a higher coercivity than media having magnetic layers deposited at lower temperatures (Cord).